In order to get possibility to connect incoming calls or transmit data to a mobile station in a cellular mobile system, it is very important that the system can locate or determine the position for the mobile station. The procedure or the function to keep count of the position of a mobile station within the mobile system is in the trade called “Location Management”, which in this text is called position management. Position management requires signalling via radio, which consequently implies that a certain part of the total radio capacity in a cellular system is needed for this type of signalling, which here for the sake of convenience is called position signalling. In order to make most possible share of the limited radio capacity possible to use for voice respective data traffic, the position management must be optimized so that it takes a minimum of the available radio resource. The degree of difficulty of the optimizing problem is increased by the fact that the mobile stations are just, as the name indicates, mobile.
In prior art the strategy for position management is to find a suitable compromise between signalling in uplink, i.e. from the mobile station to one in the mobile system permanent installed network of base stations, and signalling in downlink, i.e. from the network of base stations to a mobile station. Signalling in downlink is normally executed by searching, also called “paging”, whereby a signalling message is transmitted from the network, to search for a mobile station in a limited area, a so called “Routing Area” (RA) which consists of one or more cells. Signalling in uplink is executed by a mobile station at intervals transmitting a message to the network, which by that can keep count of where the mobile station is at the moment. Updating of the position of the mobile station is made on one hand at change of cell, which is called “Cell Update” (CU), and on the other at change of Routing Area, which in its turn consequently is called “Routing Area Update” (RAU).
In a mobile telephone system which supports packet switched services, for instance according to the specification which in English is called General Packet Radio Service and is abbreviated GPRS, the capacity and the radio resource is utilized in a comparatively cost efficient way. This is due to the fact that a given GPRS mobile station utilizes a radio channel only when there are data that shall be transmitted or received by this mobile station. In GPRS there are specified three states of a mobile station. i.e. “Idle State”, “Ready State” and “Standby State”, at which there are different operations for position management at each of the different states. In the Idle State, the mobile station is not connected to the network, and the network therefore has no information about the position of the mobile station. When the mobile station is in Ready State or in Standby State, it can, on the contrary, receive paging messages and it also can execute Routing Area Update (RAU), respective Cell Update (CU).
When the mobile station is in Ready State and it changes cell, a Cell Update (CU) is executed if the cells belong to the same routing area. If the new cell which the mobile station enters into also belongs to a new routing area, a Cell Update (CU) is executed combined with a Route Area Update (RAU). In the Ready State there are in fact two “sub-states”. Firstly “Receive/Transfer Mode”, i.e. receiving/transmission mode, which is the state that usually is used at reception respective transmission of voice respective data traffic. Secondly, “Wait Mode”, which implies one by a time parameter limited waiting state, at which the time parameter indicates a time during which the mobile station shall remain in Ready State/Wait Mode in order to later switch to Standby State. At Standby State only Routing Area Update (RAU) is executed when the mobile station changes routing area.